21. Insert the missing number.: 1, 4, 9, 16, 25, 36, 49, (….) September 6, 2025 by Admin [A]. 54 [B]. 56 [C]. 64 [D]. 81 ✅ The correct answer is option C. Numbers are 12, 22, 32, 42, 52, 62, 72. So, the next number is 82 = 64.